In order to prevent the global warming due to the release of enormous amounts of CO2, it has been studied to fixate CO2 to the submarine layer, lake bottom layer, permafrost, or the like by hydrating CO2. Meanwhile, vast amounts of CH4 hydrate lie under submarine layer or the like have been attracted as a new energy source, and thus the mining of CH4 hydrate has been studied. Further, it has been also studied to mine CH4 while fixating CO2 by substituting CH4 molecules in CH4 hydrate to CO2 molecules.
For instance, a research paper the prior art discloses the substitution of CH4 molecules in CH4 hydrate to CO2 molecules (Kazunari Ohgaki, Kiyomitsu Takano, Masairi Moritoki, “Utilization of CH.sub.4 hydrate and reservation of CO2 in Nankai trough”, Collection of Chemical Engineering Essay, Japan, 20 (1), 1994.01, pp. 121-123). In this research paper, it is discussed, thermodynamically, that methane as guest molecules in hydrate lattice is substituted to carbon dioxide without decomposing the hydrate lattice under the mixture state of CH4 gas, carbon dioxide, water, CH4 hydrate and carbon dioxide hydrate.
Further, a method for fixation of carbon dioxide has been proposed, wherein carbon dioxide is introduced to the underground CH4 hydrate layer in order to substitute methane with carbon dioxide and fixate the carbon dioxide as carbon dioxide hydrate to the hydrate layer, and extract natural gas to the Earth's surface (Japanese Patent Publication HEI 6-71161). Since a condition where CH4 hydrate exists stably also functions as a condition where carbon dioxide hydrate exists stably, the carbon dioxide hydrate can be produced by injecting gaseous or liquid carbon dioxide to the CH4 hydrate layer through a penetrating injection pipe, while by the exothermal reaction at this production the CH4 hydrate can be decomposed. Then, the methane gas is recovered to the ground through a separate exhaust pipe.
Incidentally, as a method for mining of gas hydrate, it has been proposed to emit a high speed jet flow to gas hydrate layer through a mining pipe which was impacted to the layer having the gas hydrate layer, in order to cut and break the gas hydrate and recover it as a gas including mixture fluid to the ground, while filling cavities in the layer which are created by the recovery of gas hydrate with the composition of the high speed jet flow (Japanese Patent Publication 2003-214082). As the composition of the high speed jet flow, a minute grain material which includes slime, cement type hardener, and/or industrial by-product such as blast furnace slag in slurry which is prepared by kneading water and silt, cohesive soil or the like is used.